Update ListPicker on SelectionChanged，监听ListPicker的selectItem的值变化【转】

I have two list pickers. When first list picker have selection changed it should filter data of second list picker. Second ListPicker xaml is like this

 

<TextBlockHorizontalAlignment="Left"Style="{StaticResource PhoneTextNormalStyle}"TextWrapping="Wrap"Text="text"VerticalAlignment="Bottom"/>
                <toolkit:ListPickerVerticalAlignment="Bottom"Name="CategoryList"ItemsSource="{Binding TransactionCategories, Mode=TwoWay}"SelectedItem="{Binding SelectedTransactionCategory, Mode=TwoWay}">
                <toolkit:ListPicker.ItemTemplate>
                    <DataTemplate>
                        <StackPanelOrientation="Horizontal">
                            <RectangleFill="Red"Width="24"Height="24"/>
                            <TextBlockText="{Binding CategoryName,Mode=TwoWay}"Margin="12 0 0 0"/>
                        </StackPanel>
                    </DataTemplate>
                </toolkit:ListPicker.ItemTemplate>
                <toolkit:ListPicker.FullModeItemTemplate>
                    <DataTemplate>
                        <StackPanelOrientation="Horizontal"Margin="16 21 0 20">
                            <RectangleWidth="43"Height="43"/>
                            <TextBlockText="{Binding CategoryName, Mode=TwoWay}"Margin="16 0 0 0"FontSize="43"FontFamily="{StaticResource PhoneFontFamilyLight}"TextWrapping="Wrap"/>
                        </StackPanel>
                    </DataTemplate>
                </toolkit:ListPicker.FullModeItemTemplate>
            </toolkit:ListPicker>





First picker fires the event GroupCategoryList_SelectionChanged

privatevoidGroupCategoryList_SelectionChanged(object sender,SelectionChangedEventArgs e)
    {
        var category =(TransactionGroupCategory)GroupCategoryList.SelectedItem;
        ((TransactionEditViewModel)DataContext).FilterCategoryByGroup(category.GroupCategoryId);
    }

This is a metod in ViewModel

 public  voidFilterCategoryByGroup(int groupCategoryId)
    {

        TransactionCategories=ToObservableCollection(DatabaseBl.GetData<TransactionCategory>().Where(x => x.GroupCategoryId== groupCategoryId).OrderByDescending(tc => tc.TransactionCount));
        if(TransactionCategories.Count>0)
            SelectedTransactionCategory=TransactionCategories[0];
    }

The second list picker never get refreshed in UI, even though new data was fetched through filter method. What could be wrong with this. 


原文地址：http://stackoverflow.com/questions/5466064/update-listpicker-on-selectionchanged